The present invention relates to an optical disk apparatus and, more particularly, to such apparatus for recording and/or reproducing data (such as video signal data and audio signal data) onto and/or from an optical disk which utilizes a laser beam having a wavelength of 680 (nm) or less and a lens system having a numerical aperture (NA) of 0.7 or more and arranged to have a working distance of 560 xcexcm or less so as to enable a relatively large amount of data to be recorded onto the optical disk.
Video and/or audio data may be recorded onto and/or reproduced from a number of different types of storage media such as a tape cassette and a so-called digital versatile disc (DVD). However, as hereinbelow described, the tape cassette and the DVD may have disadvantages associated therewith.
A video tape cassette for consumer use may have approximately 2 hours of data recorded thereon. Although such recording time may be acceptable for consumer use, the reproduction quality may not always be acceptable. For example, repeated use of a video tape cassette may adversely affect or even destroy data recorded on the respective tape so that upon reproduction relatively poor quality video/audio data may be provided. Additionally, the video tape cassette may not be conducive for enabling particular functions or operations, such as an easy access function, to be performed by a video tape cassette recorder/reproducer.
A rewritable type DVD may have a shape and size approximately similar to that of a compact disc (CD) and may have 2.6 GB of data (such as video and/or audio data) recorded on one face thereof. Such amount of data may only provide approximately 1 hour of recording/reproduction time. Such relatively small amount of time may be unacceptable. For example, such small amount of recording time may necessitate the need for several DVDs to record a single motion picture. As a result, such use of multiple DVDs may be inconvenient for a user or consumer.
An apparatus for recording and/or reproducing data onto/from a DVD may utilize a laser beam having a wavelength of 650 (nm) and a lens optical system having a numerical aperture of 0.6. Such apparatus may be operative to provide a number of functions or operations, such as editing, trick play, or the like. Additionally, such apparatus may utilize an effective access technique so as to enable operational modes to be quickly switched.
A DVD, used in conjunction with a DVD player, may enable relatively high quality reproduction and may facilitate the operation of a number of functions, such as an easy access function. However, to enable two hours of recording/reproducing time from one side of a DVD (so as to provide the same recording/reproducing time as with the video tape cassette) and to enable the above functions (editing, easy access, and so forth) would require approximately 8 GB of data, whereas, as previously described, a single-sided DVD may only enable 2.6 GB of data to be recorded thereon.
An object of the present invention is to provide an optical disk apparatus capable of recording a relatively large capacity of data onto an optical disk device.
More specifically, it is an object of the present invention to provide an optical disk apparatus in which user data may be recorded onto an optical disk by utilizing an optical head for irradiating a laser beam having a wavelength of approximately 680 (nm) or less to the optical disk and having a lens with a numerical aperture (NA) of approximately 0.7 or more and a working distance of approximately 560 (xcexcm) or less.
Another object of the present invention is to provide an optical disk apparatus wherein the user data is recorded onto the optical disk as a number of pits or marks in which the shortest pit length or shortest mark length is approximately 0.3 (xcexcm) or less or in which a line record density is approximately 0.23 (xcexcm/bit) or less.
A still further object of the present invention is to provide an optical disk apparatus wherein the user data is recorded onto the optical disk with a track pitch of 0.6 (xcexcm) or less.
A yet further object of the present invention is to provide an optical disk apparatus wherein the user data may be transmitted for recording onto the optical disk and for reproduction therefrom with a data transmitting speed of approximately 11.08 Mbps or more.
A still further object of the present invention is to provide an optical disk wherein redundant data is added to the user data and recorded thereto so as to provide a redundancy of approximately 23% or less.
Another object of the present invention is to provide an optical disk which includes a light transmitting layer having a thickness value within a range of 10 through 177 (xcexcm) with a discrepancy of +/xe2x88x92 xcex94t in which xcex94t is defined by xcex94t5.26(xcex/NA4) (xcexcm) wherein NA is numerical aperture and xcex is wavelength.
A still further object of the present invention is to provide an optical disk rotatably arranged in a cartridge which provides access to the optical disk.
Meandering of a groove carrying a guide groove of laser beam is varied successively in steps and a rotational speed of an optical disk is switched successively in steps in correspondence with the period of meandering.
A further object of the present invention is to provide an optical disk apparatus wherein one revolution of the optical disk is divided into a plurality of sectors based on address information which is recorded in a track, and wherein the user data is recorded in the sectors.
A further object of the present invention is to provide an optical disk apparatus wherein user data is recorded on grooves and lands of the optical disk.
A still further object of the present invention is to provide an optical disk apparatus having a buffer memory wherein a speed of transmitting the user data for recording onto the optical disk is greater than a speed at which the data is supplied to the buffer memory and/or wherein a speed of transmitting the user data reproduced from the optical disk is greater than a speed at which the data is supplied from the buffer memory.
A further object of the present invention is to provide an optical disk apparatus wherein user data is arranged in predetermined blocks and an error correction code is added thereto, and wherein the user data is recorded to or reproduced from an optical disk in one or more blocks in which a block has 32 or more KB.
In accordance with an aspect of the present invention, an optical disk apparatus for recording and/or reproducing user data onto and/or from an optical disk is provided which has an optical head for irradiating a laser beam having a wavelength of approximately 680 (nm) or less to the optical disk and having a lens with a numerical aperture (NA) of approximately 0.7 or more and a working distance of approximately 560 (xcexcm) or less.
The present optical disk apparatus may record user data having a spot size approximately one half that of a DVD so as to provide relatively high recording density. As a result, such optical disk apparatus, when utilizing a Partial-Response Maximum-Likelihood (PRML) technique or the like or when the redundancy is reduced by using premastered address having relatively high efficiency and the like, may provide a recording capacity of approximately 8 GB on an optical disk. By setting the working distance to a relatively small value, an optical system may be formed by a lens having a small aperture and a relatively high numerical aperture of 0.7 or more. Further, in this situation, allowable center eccentricity between the lens faces and allowable face angle may be set to practical ranges. As an example, in this situation, when the working distance is set to 560 xcexcm or less, a laser beam may be incident on an object lens with a beam diameter of 4.5 (mm) or less which is similar to a value utilized with a DVD.
The shortest pit length associated with a DVD may be 0.4 xcexcm. However, by utilizing the present optical disk apparatus with its numerical aperture, the shortest pit length or the shortest mark length may have a value of approximately 0.3 xcexcm. By using a shortest pit length or shortest mark length of 0.3 xcexcm or less, a recording capacity of approximately 8 GB on an optical disk may be obtained. Further, when a so-called (1, 7) RLL modulation technique is applied thereto, a line density of approximately 0.23 xcexcm/bit may be obtained, and when a PRML technique or the like is applied, a line density of approximately 0.23 xcexcm/bit or less may be achieved. With a line density of 0.23 xcexcm/bit, a recording capacity of approximately 8 GB on an optical disk may be obtained.
When the above relationships are used, a track pitch may be determined having a value of 0.6 (xcexcm) which still provides a recording capacity of 8 GB.
Further, when the data transmitting speed is set to 11.08 (Mbps) or more, a continuous video signal may be recorded and/or reproduced while maintaining sufficient time period in seeking or the like even wherein the recording involves multiplexing an audio signal and a video signal which has been subjected to data compression by a MPEG2 technique in which a rate of 6 Mbps or more is needed for images.
Furthermore, user data may be efficiently recorded by adding redundant data so as to perform a recording operation with a redundancy of 23% or less.
When an optical disk is accessed by an optical system having a relatively high numerical aperture, a skew margin of the optical disk may be reduced or compensated for by reducing the thickness of a light transmitting layer. In this situation, stable access may be provided to an optical disk by providing a light transmitting layer with a thickness value within a range of 10 through 177 (xcexcm) with a discrepancy of +/xe2x88x92 xcex94t in which xcex94t is defined by xcex94txe2x89xa65.26 (xcex/NA4) xcexcm wherein NA is numerical aperture and xcex is wavelength.
Further, dust or a defect on the surface of the optical disk may have an adverse affect or influence on the data recorded thereon. For example, dust having a size of 100 xcexcm or more may produce a so-called burst error. However, storing such optical disk in a cartridge which enables access to the optical disk for an optical system may prevent or reduce the exposure of the optical disk to dust and the like so as to prevent or reduce adverse affects which may be otherwise caused by dust and the like. Additionally, such cartridge may protect the optical disk from scratches and other types of damage.
Furthermore, when meandering of a groove varies successively in steps and a rotational speed of an optical disk switches successively in steps in correspondence with the period of meandering, access may be provided to an optical disk by a so-called Zoned Constant Linear Velocity (ZCLV) technique. As a result, desired data may be efficiently recorded using an information recording face of the optical disk and lowering of access speed may be effectively avoided.
Additionally, when one revolution of an optical disk is divided into a plurality of sectors and user data is recorded in the sectors, access speed thereto may be improved.
Further, by recording information on both lands and grooves, an optical disk having a relatively narrow track pitch may be simply fabricated and a tracking error signal may be detected with a satisfactory signal-to-noise (SN) ratio.
Furthermore, when the speed of transmitting user data for recording onto an optical disk or the speed of transmitting data reproduced from an optical disk and inputting to a buffer memory is greater than a speed at which the data is supplied to a buffer memory or the speed at which the data is outputted from the buffer memory, processing of a substitution(s) of a defect sector may be executed and functions such as simultaneous recording and reproducing, postrecording and the like may be performed.
Additionally, error correction processing may be improved by performing such processing with a block having a size of 32 KB or more.